SndsoftheSbrbs

My check engine light came on. My code reader gave me a code P22A1. I cannot find much information on it. It is not listed under Mercedes-Benz codes that I have found. My code reader indicates that it is related to the nitrogen oxide sensor. Any thoughts? I'm very disappointed.

http://obdii.pro/en/code/P22A1

SndsoftheSbrbs

http://www.benzworld.org/forums/w251...50-diesel.html

SndsoftheSbrbs

My mechanic says that problems associated with this code are hard to diagnose.

CedarMtn

The thread you referenced is for an adblue heater error code which is different from your original post.

If you are getting a code related to the adblue heater then you will find that it is very hard to diagnose. I had a repetitive problem with this code and my dealer did several fixes (under warranty) that would have been prohibitively expensive if I had to pay. These included replacing the heater, replacing the wiring harness and other work done over many service calls. CEL kept coming back with the same error code after every fix. In the end, it was a faulty crimp connector causing an error code to be thrown, which caused the CEL to be on. So after all that work, simply re-crimping this connector solved the problem.

I had a thread on the other W251 user forum website which described the problem. Here's a partial copy of my post which described the fix (note this might not be your problem but is the least expensive thing to check first when you get an error code related to the Adblue heating system):

"The last time (after the wiring harness was replaced) I took it back last week and the dealer then performed a wire by wire continuity test on all electrical related to the Adblue system. THIS is when they discovered that there was a loose connection (K27 terminal and F37 fuse block). It was K27 terminal which was loose (Loose blade connector). Once this was re-crimped, the problem went away!!! I have driven for one week and no problem. ****This might be a good place to start the trouble shooting, especially if the work is not covered under warranty. Might save a lot of parts and time.****

Edit: All the continuity tests were performed while manipulating the harness, connections - the problem was discovered when manipulating the relay K27 and F37 fuse block. I suspect this was the problem all the time, since the light would come on after a few miles drive (hitting some bumps caused a spike which throws the error code and turns on the CEL light).

Note: throughout, the car ran great - just with the CEL light on."

SndsoftheSbrbs

I am receiving the P22A1 code in 11 degree weather.

SndsoftheSbrbs

I am apparently looking at $2,000 to start with replacing these expensive sensors.

SndsoftheSbrbs

I got my baby back. She had her NOx sensors replaced and camshaft position sensor replaced. Unfortunately, it looks like the timing chain and tensioners will need to be replaced in the near future.

auto385

How many miles on your machine. With proper oil changes, the chains should never need replacing. On many vehicles at my shop I only see chain failures with vehicles that haven't been maintained properly, and I don't mean following the manufacturers schedule. These schedules are way too long between oil changes. And I don't care what kind of oil you use. Oil changes every 4000miles would be proper.

SndsoftheSbrbs

Roughly 78k miles. I can't speak to how often it was serviced. It was not always in my personal possession.

auto385

Who told you that the chains need replacing?

SndsoftheSbrbs

My factory-trained mechanic told me that the chains need to be replaced.

The car sometimes makes a slapping noise immediately after start-up, which is often a symptom of timing chain and/or tensioner issues. He said it had a hard time starting up a couple of times while in his shop. I've never had trouble starting the car, for what it's worth, even in below zero weather.

chsu74

https://mbworld.org/forums/gl-class-...placement.html